Jean-Philippe Mateta struck for Palace, but Beto and Charly Alcaraz scored the goals for Everton in their 2-1 win.
Hughes said, "It is raw now. Very frustrating. Goals avoidable, frustrating night."
"I don't think we were at our best, even in the first half. Everton are difficult to break down. Giving them a (first) goal like that it was always difficult to get back in the game. Little details have let us down, again.
"I think we needed something different on the pitch and it worked for the start of the second half. They hit us with a sucker punch at the end which is frustrating.
"There's plenty of errors leading to goals. Our home form has been poor this season. Our away form this season has been top.
"It needs to change quickly.
"I can't put my finger on it or it would have changed a long time ago."